1. Field of the Invention
The present invention relates to a semiconductor device, in particular, the present invention relates to a light emitting device having a light emitting element formed on a substrate having an insulating surface and method of manufacturing thereof. Further, the present invention relates to an organic light emitting module on which ICs and the like, including a controller, are mounted to an organic light emitting panel. Note that the terms organic light emitting panel and organic light emitting module both generically refer to light emitting devices in this specification. The present invention additionally relates to an apparatus for manufacturing the light emitting device.
In this specification, semiconductor devices correspond to general devices functioning by use of semiconductor characteristics. Therefore, a light emitting device, an electro-optical device, a semiconductor circuit and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
In recent years, techniques of forming TFTs (thin film transistors) on substrates have been progressing greatly, and developments in their application to active matrix type display devices is advancing. In particular, TFTs that use polysilicon films have a higher electric field effect mobility (also referred to as a mobility) than TFTs that use conventional amorphous silicon films, and therefore high speed operation is possible. Developments in performing control of pixels by forming driver circuits made from TFTs that use polysilicon films on a substrate on which the pixels are formed have therefore been flourishing.
It has been expected that various advantages can be obtained by using active matrix type display devices in which pixels and driver circuits are mounted on the same substrate, such as reductions in manufacturing cost, miniaturization of the display device, increases in yield, and reductions in throughput.
Furthermore, research on active matrix type light emitting devices using organic light emitting elements as self light emitting elements (hereinafter referred to simply as light emitting devices) has become more active.
Switching elements composed of TFTs (hereinafter referred to as switching elements) are formed for each pixel in active matrix type light emitting devices, and driver elements for performing electric current control by the switching TFTs (hereinafter referred to as electric current control TFTs) are operated, thus making EL layers (specifically, light emitting layers) emit light. For example, a light emitting device disclosed in Japan Patent Laid-Open No. 10-189252 A is known.
Organic light emitting elements are self light emitting, and therefore have high visibility. Backlights, necessary for liquid crystal display devices (LCDs), are not required for organic light emitting elements, which are optimal for making display devices thinner and have no limitations in viewing angle. Light emitting devices using the organic light emitting elements are consequently being focused upon as substitutes for CRTs and LCDs.
Note that EL elements have a layer containing an organic compound in which luminescence develops by the addition of an electric field (electroluminescence) (hereinafter referred to as EL layer), an anode, and a cathode. There is light emission when returning to a base state from a singlet excitation state (fluorescence), and light emission when returning to a base state from a triplet excitation state (phosphorescence) in the organic compound layer, and it is possible to apply both types of light emission to light emitting devices manufactured by the manufacturing apparatus and film formation method of the present invention.
The EL elements have a structure in which an EL layer is sandwiched between a pair of electrodes, and the EL layer normally has a laminate structure.
A laminate structure of “a hole transporting layer/a light emitting layer/electron transporting layer” can be given as a typical example. This structure has extremely high light emitting efficiency, and at present almost all light emitting devices undergoing research and development employ this structure.
Further, a structure in which: a hole injecting layer, a hole transporting layer, a light emitting layer, and an electron transporting layer are laminated in order on an anode; or a hole injecting layer, a hole transporting layer, alight emitting layer, an electron transporting layer, and an electron injecting layer are laminated in order on an anode may also be used. Fluorescent pigments and the like may also be doped into the light emitting layers. Further, all of the layers may be formed by using low molecular weight materials, and all of the layers may be formed by using high molecular weight materials.